This invention relates to a process for preparing 6-substituted 4-chromanones from phenolic acrylate ester compounds derivable from para-substituted phenolic compounds and beta-unsubstituted acrylic acid compounds which are esterifiable therewith. The 6-substituted 4-chromanones prepared by the process of this invention are useful as intermediates for preparing pharmaceutical agents.
Preparation of 4-chromanones via condensation of beta-substituted, beta,beta-disubstituted and alpha, beta-disubstituted acrylic acids with phenolic compounds in anhydrous hydrogen fluoride is disclosed by Offe and Barkow in Chem. Ber. 80, 458 (1947), hereinafter Offe I. However, Offe I does not disclose such preparation using beta-unsubstituted acrylic acids. Offe and Barkow indicate in Chem. Ber. 80, 464 (1947), hereinafter Offe II, that it is possible but not practical to prepare 4-chromanones in hydrogen fluoride from phenol and beta-unsubstituted acrylic acid compounds such as acrylic acid per se. Offe II does not disclose how such preparation is possible. Similarly, Amakasu and Sato indicate in J. Org. Chem. 31, 1433 (1966) that 4-chromanones are not obtainable via reaction of acrylic acid or alpha-monosubstituted acrylic acid with phenols.